Linux powers the fastest computers on the planet

"To be exact, 391 are running their own house-brand of
Linux. 62 are running one version or another of Novell's SUSE
Linux, including such variants as UNICOS/lc and CNL (Compute Node
Linux). Red Hat and its relatives, including CentOS, comes in
second with 16 supercomputers.

"As for the non-Linux members of the fastest computer club,
IBM's AIX Unix, with 22 computers, is the only serious competitor.
Microsoft and Sun, with Windows HPC 2008 and OpenSolaris are barely
in the running with 5 supercomputers for Windows and a mere pair
for OpenSolaris."